Endocrinology, Vol 137, 1265-1271, Copyright © 1996 by Endocrine Society

ARTICLES

Testosterone is required for gonadotropin-releasing hormone stimulation of luteinizing hormone-beta messenger ribonucleic acid expression in female rats

M Yasin, AC Dalkin, DJ Haisenleder and JC Marshall
Department of Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA.

Pulsatile GnRH stimulates the synthesis and secretion of LH and FSH in both male and female rats. In the male rat, exogenous GnRH pulses increase alpha, LH and FSH beta messenger RNAs (mRNAs) 3-fold within 24 h. In contrast, the results of recent in vivo and in vitro studies have shown that GnRH stimulates an increase in alpha and FSH beta mRNAs, but not LHbeta. However, during the estrous cycle, LHbeta mRNA increases during the GnRH-induced LH surge on proestrus afternoon. This increase in LHbeta mRNA appears to be coincident with a transient rise in serum testosterone (T). Therefore, the present study was conducted to determine whether T has a role in facilitating GnRH stimulation of LHbeta mRNA expression. In the first group of studies, adult female rats were ovariectomized, and T implants were inserted sc 7 days before the study (serum T, 1.86 ng/ml). Animals received iv pulses of GnRH (25 ng; 30-min interval) for 6-24 h (saline pulses to controls). The data showed that in the presence of T, GnRH stimulated a significant increase in LHbeta (as well as alpha and FSH beta) mRNAs within 6 h (P < 0.05 vs. saline-pulsed controls). Other results revealed that T treatment was critical to the stimulatory effect of GnRH on LH beta mRNA. A second group of studies examined the time course and dose effects of T on LH beta mRNA expression. Maximal LH beta mRNA responses to GnRH (3-fold increase vs. saline controls; P < 0.05) were seen after pretreatment with the lowest dose of T examined (serum T, 0.42 ng/ml), which is similar to T concentrations on proestrus. Higher doses of T suppressed LH release, as well as LH mRNA responses to GnRH. The T- induced LHbeta mRNA response to pulsatile GnRH was seen within 24 h of exposure to T and was the result of an androgenic action, as similar results were observed in rats that received dihydrotestosterone. These findings suggest that T is required to facilitate GnRH stimulation of LHbeta mRNA in the female rat. Moreover, in the presence of the concentrations of T seen on proestrus, LHbeta mRNA increases within 6 h, which is similar to the time course seen during the LH surge. Thus, the present results also suggest that the combined effects of the rise in serum T and increased GnRH secretion induce the rapid rise in LHbeta mRNA expression on the afternoon of proestrus.

This article has been cited by other articles:

				L. L. Burger, D. J. Haisenleder, G. M. Wotton, K. W. Aylor, A. C. Dalkin, and J. C. Marshall The regulation of FSHbeta transcription by gonadal steroids: testosterone and estradiol modulation of the activin intracellular signaling pathway Am J Physiol Endocrinol Metab, July 1, 2007; 293(1): E277 - E285. [Abstract] [Full Text] [PDF]

				D.J. Haisenleder, L.L. Burger, K.W. Aylor, A.C. Dalkin, H.E. Walsh, M.A. Shupnik, and J.C. Marshall Testosterone Stimulates Follicle-Stimulating Hormone {beta} Transcription via Activation of Extracellular Signal-Regulated Kinase: Evidence in Rat Pituitary Cells Biol Reprod, March 1, 2005; 72(3): 523 - 529. [Abstract] [Full Text] [PDF]

				L L Burger, D J Haisenleder, A C Dalkin, and J C Marshall Regulation of gonadotropin subunit gene transcription J. Mol. Endocrinol., December 1, 2004; 33(3): 559 - 584. [Abstract] [Full Text] [PDF]

				D. Curtin, S. Jenkins, N. Farmer, A. C. Anderson, D. J. Haisenleder, E. Rissman, E. M. Wilson, and M. A. Shupnik Androgen Suppression of GnRH-Stimulated Rat LH{beta} Gene Transcription Occurs Through Sp1 Sites in the Distal GnRH-Responsive Promoter Region Mol. Endocrinol., November 1, 2001; 15(11): 1906 - 1917. [Abstract] [Full Text] [PDF]

				J. L. Turgeon and D. W. Waring Androgen Modulation of Luteinizing Hormone Secretion by Female Rat Gonadotropes Endocrinology, April 1, 1999; 140(4): 1767 - 1774. [Abstract] [Full Text]

				A. C. Dalkin, D. J. Haisenleder, J. T. Gilrain, K. Aylor, M. Yasin, and J. C. Marshall Gonadotropin-Releasing Hormone Regulation of Gonadotropin Subunit Gene Expression in Female Rats: Actions on Follicle-Stimulating Hormone {beta} Messenger Ribonucleic Acid (mRNA) Involve Differential Expression of Pituitary Activin ({beta}-B) and Follistatin mRNAs Endocrinology, February 1, 1999; 140(2): 903 - 908. [Abstract] [Full Text]

				D. J. Haisenleder, M. E. Cox, S. J. Parsons, and J. C. Marshall Gonadotropin-Releasing Hormone Pulses Are Required to Maintain Activation of Mitogen-Activated Protein Kinase: Role in Stimulation of Gonadotrope Gene Expression Endocrinology, July 1, 1998; 139(7): 3104 - 3111. [Abstract] [Full Text] [PDF]

				D. J. Haisenleder, M. Yasin, and J. C. Marshall Gonadotropin Subunit and Gonadotropin-Releasing Hormone Receptor Gene Expression Are Regulated by Alterations in the Frequency of Calcium Pulsatile Signals Endocrinology, December 1, 1997; 138(12): 5227 - 5230. [Abstract] [Full Text] [PDF]

				U. B. Kaiser, A. Jakubowiak, A. Steinberger, and W. W. Chin Differential Effects of Gonadotropin-Releasing Hormone (GnRH) Pulse Frequency on Gonadotropin Subunit and GnRH Receptor Messenger Ribonucleic Acid Levels in Vitro Endocrinology, March 1, 1997; 138(3): 1224 - 1231. [Abstract] [Full Text] [PDF]